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Long Sands Beach, York
Background geology and characteristics
Annual and seasonal beach profile changes
At Long Sands Beach, all profiles start from a seawall. The data available at LS1 were from 2001-2002, and 2005-2007. It appears that a different starting point was used at LS1 for 2001-2002 data collection, and data from 2003-2004 were not entered into the online database (Figure 154). From 2001-2002, LS1 experienced slight lowering adjacent to the seawall, but berm growth at about the 30 m mark. From 2005-2006, the upper portion of the profile (from about 70 m from the mark landward, or about an elevation of 0.6 m NAVD) underwent slight recession and scarping adjacent to the wall. During the same time, seaward of the 70 m mark, the beach accreted. In 2007, the upper portion of the profile, from about 100 m from the mark landward, accreted back to a 2005 position, while seaward of 100 m, some erosion occurred. Seasonal data (Figure 155) show that the winter profile had much more sediment than the summer profile; this may be due to skewing of data since two different starting benchmarks were used (i.e., 2001-2002, and 2005-2007). The standard deviation data (Figure 156a) show that both summer and winter profiles undergo about the same amount of variation, on the order of 20-30 cm, along the entire length of the profile.
At LS2, data were only available from 2005-2007. During this period, the profile appears to have undergone consistent accretion along its entire length (Figure 157). Seasonal data show little prominent summer berm development (Figure 158), though there appears to be a slightly larger volume of sediment on the upper portion of the profile (within 20 m of the mark) during the summer. Standard deviation data (Figure 156b) indicate similar variability (20-30 cm) between summer and winter (slightly higher in summer) along the entire profile.
LS3 demonstrates a marked break in slope for all profiles at the 40 m from the pin mark, at an elevation around 1 m NAVD (Figure 159). This may mark the base of the seawall or an underlying substrate that is difficult to erode, or for sediment that is trying to migrate onshore to move past. From 2005-2006, slight accretion occurred at the top of the profile, while seaward of the 40 m mark, the beach deepened about 30 cm until the 90 m mark, where the 2006 and 2005 profiles became quite similar again. In 2007, accretion occurred, with the beach seaward of the 40 m mark gaining approximately 50 cm in elevation between 2006-2007. Seasonally, LS3 exhibits a more varied summer profile in terms of topography along the upper portion of the profile, and a greater volume of sediment starting at the 40 m mark (Figure 160). The standard deviation data (Figure 156c) indicate that the profile undergoes more variability during the winter, especially between the 40-95 m area, ranging from about 40-50 cm vertically. The summer profile varies only by about 20 cm until offshore (at 90 m), where variability approaches that of the winter profile. This seasonable difference is likely due to different incoming wave directions and the interannual variability in sand bar locations.
At LS4, data were available from 2002, and 2004-2007. Like LS3, the upper portions of the profile are quite similar until a marked inflection point at around the 20 m mark (elevation between 0 and 1 m NAVD); again, this may mark a hard bottom, base of seawall, or some less erodable underlying surface (Figure 161). From 2002-2004, the entire profile gained elevation, with the most notable changes seaward of the 20 m mark. Little change occurred from 2004-2005, and apparently the profile eroded slightly between 2005-2006. In 2007, accretion added sediment to the profile seaward of the 20 m mark. The summer mean profile exhibits a greater concentration of sand along the profile from about the 20 m mark seaward (Figure 162). There is more variability in the winter profile at around the 10 m mark (about 30 cm vertically), though the standard deviations of the summer and winter profiles stay similar seaward of this, with around 20 cm of vertical variability (Figure 156d).
The beaches at Long Sands Beach generally appear to be stable to accretional. The profiles are generally flat, with little prominent berm features. This may be caused by the large seawall that fronts the entire beach - which precludes landward migration of the beach and dune system. Since many high tides reach the seawall (it is a regularly "active" structure reflecting waves back seaward across the profile) a solid "four-season berm" does not have the chance to develop along this type of beach. The limited amount of sediment within this beach system means that seasonal variation - summer beach and winter bar formation - is imperative for the beach to maintain itself. If significant sediment is lost offshore, the lowered profile may not fully recover.
Last updated on January 3, 2008
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